class RSpec::Core::Configuration

def raise_on_warning=(value)

end
rspec.raise_on_warning = true
RSpec.configure do |rspec|

@example

you want RSpec to run in a 'strict' no warning situation.
Turns warnings into errors. This can be useful when 
def raise_on_warning=(value)
  if value
    RSpec::Support.warning_notifier = RAISE_ERROR_WARNING_NOTIFIER
  else
    RSpec::Support.warning_notifier = RSpec::Support::DEFAULT_WARNING_NOTIFIER
  end
end